Check engine light on and battery keeps dying. Bad battery or Alternator?
It could be one the other or both, Charge the battery if you can, after the charge check to see if you have 12 Volts and then start the car and let it run for about 1/2 Hour. Stop the car and check the volts on the battery if it not 12 Volts then the Alternator is not charging and draining the battery
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